In the general area of recreational vehicle, particularly marine pleasure vessels, on-board water storage tanks are commonly used to provide water for use within the vehicle. The internal water supply systems commonly used in such vehicles are low pressure systems that rely on low pressure pumps to distribute water from atmospheric-pressure water storage tanks. Vehicles such as pleasure boats may be moored for extended periods of time and it is a necessity that means are provided for refilling on-board water storage tanks from an external source, such as a public water supply system.
Usually, in the case of a moored pleasure boat, a garden-type hose is connected to a dockside water tap and water, at a relatively high supply pressure, is directed into an on-board tank through a deck-mounted filler tube. When the tank is filled, the supply water tap is simply turned off. If the boat is moored for extended periods of time while being occupied, the repeated refilling required become tedious and are often ignored until the on-board tank runs dry at some inopportune time. However, because the typical pleasure boat plumbing system is not designed to withstand the pressures of external water supply systems, it is not safe to leave the supply hose connected and the water supply turned on continuously. Obviously, an on-board leak in the plumbing system could have disastrous consequences and is to be avoided regardless of the inconvenience of having to manually refill the water tank periodically.
Some automatic water refilling systems have been proposed. These, however, require that the on-board plumbing system be modified to accommodate a relatively high pressure, constant source of external water. There are inherent safety problems in such by-pass plumbing systems and many boaters are unwilling to risk the chance that one of the internal fittings might rupture due to being exposed to constant "city" water pressure. A break in any such fitting, or a failure in an on-board control valve that would direct that water pressure to unsuited parts of the plumbing, could cause the boat to sink. Therefore, prudent boaters must still take care to turn the external water supply completely off for safety's sake when leaving their boat.